The primary objective of this application is to refine and test a practical, high-resolution, three-dimensional (3D) radiographic system that can be applied interactively in task-dependent ways and which precludes incidental opportunities for data loss while minimizing patient exposure to ionizing radiation. The new design also permits the patient to move freely between exposures with no resulting degradation of the reconstructed image. This is to be accomplished through integration of an arbitrary number of x-ray projections exposed using projection angles selected empirically by the operator to match the diagnostic task. The 3-D integration is to be accomplished with the aid of a new tomosynthetic reconstruction scheme called tuned-aperture computed tomography (TACT). This general method is based on an extension of optical aperture theory, and it provides a conceptual bridge between conventional transmission radiography and computed tomography. The specific aim is to test TACT using a second-generation 3-D x-ray system which augments the capability for improved performance already demonstrated from an existing first-generation prototype. This is to be accomplished by altering the design of this prototype in ways that reduce its complexity while significantly increasing its versatility and its potential for operation at reduced exposures to ionizing radiation. This system is to be tested in vitro using cadaver specimens and challenging (projection-sensitive) teaching phantoms. Trained dentists and dental x-ray technicians shall produce and interpret the resulting images. These data are to be compared with those obtained from the existing first-generation prototype and conventional two dimensional film-based intraoral control images. Performance will be assessed by determining if the diagnostic yield per exposure can be improved significantly over the status quo for selected tasks of diagnostic interest.